Upon demand of customers, the car manufacturers present more and more vehicle models in a so-called three-door vehicle type with two side doors and a hatch-back. Actually, this construction provides vehicles of a smaller length which are more suitable in city traffic, while permitting however the transportation of at least four persons since the rear portion of the vehicle is provided with a single back seat or the like.
However, the above type of vehicles requires necessarily side doors of a great length in order to make it easier for the rear passengers to get in and out of the vehicle.
But it is also necessary to provide front seats (for the driver and front passenger) with the back portions foldable onto the sitting portions so as to permit an easy passage of the rear passengers, both in getting into and out of the vehicle.
It has been known for a long time to provide the back portions of the front seats of vehicles so as to be adjustable in their inclination for providing a maximum comfort for the driver and the front passenger.
Articulation mechanisms enabling such adjustments in inclination of the back portion are therefore conventional means. These mechanisms can also be designed in such a manner as to allow the folding of these back portions onto the sitting portions, with an additional memory member for returning the back portion into its correct position once the rear passengers have entered or exited from the vehicle being provided. However all these adjusting devices are complex and therefore very expensive.
This is particularly the case for the devices shown in EP-A-0,250,290 (Cousin) and FR-A-2,231,538 (Keiper), with the latter prior art document disclosing a positioning means using toothed blocks locked into the toothing of a ring by means of a cam which is returned on latching by means of curved slots actuating them via pins rigidly connected to these blocks. But nothing in this known arrangement retains the blocks over a certain angular range in order to keep them disengaged with the toothing of the ring.
Car manufacturers have long been searching for a very reliable, simple and rather cheap mechanism, which is mountable on various types of seats and which has the following necessary basic functions: i) an adjustment of the inclination of the seat back portion with respect to the sitting portion, and ii) a rapid folding of the back portion onto the sitting portion with a memory member for returning the seat back portion to its correct position once the vehicle rear passengers have entered or exited the vehicle.
Finally, these mechanisms have to be embodied such as to be adaptable to various types of vehicles and to be controllable in a simple manner, both for the adjustment in inclination of the back portion and for folding the back portion onto the sitting portion.
Moreover, these mechanisms must be free of any notable play so as to avoid discomfort for the passenger sitting on the respective seat.